Electronic structure of the LaS surface and LaS/CdS interface

Abstract

The electronic structure of the LaS surface and CdS/LaS interface is calculated by means of a first-principles electronic-structure method for slab and bulk geometries. The calculations were based on the local-density approximation to density-functional theory and made use of linear muffin-tin orbitals as basis functions for solving the Kohn-Sham equations. The observed low work function of LaS is reproduced by our theory and the calculated surface relaxation of LaS is found to be very small. It is further found that NaCl structured layers of LaS should grow in a well-behaved, epitaxial way on a CdS substrate with a ZnS structure. The interlayer spacing between the first atomic layer of LaS and the topmost layer of the CdS substrate is found to be close to the interlayer distances in both LaS and CdS. The LaS/CdS geometry should thus be possible to grow, and may be a good candidate for cold electron emitter devices.